Electrochemical lithium intercalation into multiwall carbon nanotubes: a micro-Raman study

The electrochemical intercalation of lithium into carbon electrodes containing multiwall carbon nanotubes produced by electric arc technique was carried out in button cells in different electrolytes. An exfoliation of graphene layers was observed with the electrolyte LiPF6 (1M) dissolved in ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC) (1:1:3 by volume). Raman spectra were recorded to elucidate the lithium intercalation mechanisms of multiwall nanotubes. The spectral changes of the Raman E2g band showed that the lithium was intercalated between graphene layers of carbon nanotubes without the formation of n-staged phases with n higher than 2 in contrast to the intercalation into graphite which proceeds via the formation of staged graphite intercalation compounds.